Electrical Conduction Mechanism Research Articles

On the structural and electrical properties of MgFe2O4, MgMn0.2Fe1.8O4, and Mn3O4

Charge carrier transport via donor/acceptor pairs of similar elements is dominant in n-type MgFe2O4 and p-type Mn3O4 spinels. The temperature-independent activation energy in the form of the nearest neighbor hopping model is applied for Fe2+/Fe3+ pairs of cubic MgFe2O4 spinel in the temperature range of 423–523 K (150–250 °C). At such high temperatures, even for this relatively narrow temperature range, the constant energy barrier deviates to a variable range hopping energy barrier in the case of Mn3O4, due to Jahn-Teller active octahedral sites. Replacing 10 mol% of Fe at octahedral sites with Mn has significantly increased the electron hopping energy barrier and electrical conductivity of MgFe2O4, while keeping the nearest neighbor hopping model dominant. The observed high energy barrier is due to donor/acceptor pairs of different elements (Mn/Fe). Due to a lack of structural distortion, deviation from the nearest neighbor hopping mechanism with temperature-independent activation energy was not observed. Rietveld refined XRD patterns and FT-IR spectra are utilized to support the argument on electrical conductivity mechanisms.

Dielectric Relaxation Behavior and Electrical Conduction Mechanism of PVA/ZnO Nanocomposites for Flexible Electronic Device Application

Transport properties of polyvinyl alcohol/ZnO nanocomposites (PVA/ZnO) of varying ZnO nanofiller are studied focussing on their potential application in electronic device application. The structural, morphological, and elemental composition studies of the prepared samples are done by X‐ray diffraction (XRD), scanning electron microscope (SEM), and energy‐dispersive X‐ray analysis (EDX). XRD confirms the formation of nanocomposites. SEM image shows the dispersion of ZnO nanoparticles on the surface of PVA matrix. EDX verifies that no external impurities are present in the nanocomposite samples. Frequency‐ and temperature‐dependent dielectric measurement of the samples reveals maximum dielectric constant at PVA/15 wt% ZnO nanocomposite. Dielectric loss results show a lossless behavior at higher frequencies (<0.2), indicating their suitability for high‐frequency applications. The AC conductivity studies reveal that electrical conduction mechanism in the nanocomposites is governed by the correlated barrier hopping mechanism. Activation energy of the samples reveals the presence of two thermally activated transport mechanism above and below 353 K. The imaginary part of electric modulus with frequency shows a single relaxation peak indicating the transition from long‐range to short‐range mobility with increasing frequency and temperature above 353 K. The contribution of grain and grain boundary in the electrical conduction process is confirmed from the Nyquist plot.

Temperature Dependence of Electrical Properties and Conduction Mechanism of SiNx‐Based Resistive Random Access Memory

Herein, the effect of temperature on the switching characteristics and the conduction mechanism of the Ti/SiNx/Pt resistive random access memory device is investigated. The switching behavior of the device is investigated by comparing the I–V curves of the device in the temperature range of RT‐653 K. The temperature dependence of the current and the conduction mechanism of the device within RT‐463 K is investigated. It is found that the device exhibits good bipolar switching behavior in the temperature range of RT‐463 K, and the low resistance state (LRS) current and high resistance state (HRS) current show an increasing and then decreasing trend with increasing temperature. There is a stronger temperature dependence of the LRS current and the conduction mechanism from ohmic conduction to Schottky emission under LRS, which is attributed to the involvement of the reactive electrode Ti in the reaction at a certain temperature and the generation of a TiNx layer. Based on the above phenomenon, it is believed that not only the temperature affects the reliability of the device, but also the influence of reactive electrodes cannot be ignored. This article provides a reference for further preparation of SiNx‐based resistive random access memory devices with higher reliability and wider temperature usage range.

Bis(DMAP) cobalt(II) porphyrin complexes: Dielectric properties and visible light irradiated photocatalytic degradation of toluidine blue studies

Two novel cobalt(II) tetraphenylporphyrin-based six-coordinate complexes; bis(4-Dimethylaminopyridine)(5,10,15,20-tetrakis[4-bromophenyl]porphinato) cobalt(II) (1) and bis(4-Dimethylaminopyridine) (5,10,15,20-tetrakis[4-chlorophenyl]porphinato)cobalt(II) (2) were synthesised in good qualitative and quantitative yields. The chemical structures of these synthesized compounds were confirmed by elemental analysis, infrared, proton nuclear magnetic resonance and mass spectrometry, UV–vis absorption, and fluorescence spectroscopies. Their photophysical properties, namely their molar extinction coefficients (ε), fluorescence quantum yields (Φf) and lifetimes (τf), were determined and compared with those of meso-tetraphenylporphyrin. The dielectric properties such as dielectric constant (ε′), dielectric loss (ε″), and conductivity (σ) were investigated as a function of temperature and frequency. Impedance analysis was carried out using Cole-Cole plots to understand the electrical conduction mechanism. As an application of our two cobaltous complexes, an investigation involving complexes 1–2 in the photocatalytic performance was carried out by decomposing the TB dye under visible light irradiation at room temperature.

Electrical performance and conductive mechanism of xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 ceramics with NTC effect via chemical modification

xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 (xLCO-(1-x)BCTS) ceramics were manufactured using a solid-phase reaction method. All samples exhibited single cubic perovskite structures and a typical negative temperature coefficient (NTC) effect. The grain sizes increased with increasing LCO doping content. For all samples, the resistivities (ρ25), activation energies for electrical conduction (Ea), thermal constants (B25/75), and activation energies of the relaxation process (Erelax) were in the ranges of 5.93 × 104-9.36 × 108 Ω•cm, 0.3700–0.2951 eV, 3177–3988 K, and 0.3539–0.2890 eV, respectively. Such a combination of ρ and B renders these materials to be potential candidates for NTC thermistors. According to the XPS spectra and due to the difference in ion radius among Co3+, Co4+, Ti3+, and Ti4+, Co3+-O-Co2+ and Ti3+-O-Ti4+ bonds were formed, and the electrons in the continuous bonds generated jumping conduction. The fitted results of the equivalent circuit showed that Rg and Rgb decreased with increasing LCO content, which is consistent with the DC resistivity at 25 °C. The results of the analysis indicate that the conductive mechanism of xLCO-(1-x)BCTS ceramics was electron hopping conduction.

Electrical and optical properties of polyamide 6 nanocomposites with multi-walled carbon nanotubes

In this work, quantum chemical modeling, electrical conductivity, Raman scattering, and photoluminescence of polyamide 6 nanocomposites with multi-walled carbon nanotubes (0–2.5 vol%) were investigated. It was shown that the concentration dependence of the electrical conductivity obeys the percolation theory and has the value of percolation threshold 1.41 vol%. The conductivity value of the composite at 2.5 vol% nanotubes is 1.1*10-3 S/cm. It was found that in PA6 nanocomposites filled with MWCNT an increase in the concentration of nanotubes from 0.001 to 0.015 vol%, namely in the pre-percolation region of electrical conductivity, due to a significant restructuring of the Raman spectra, which consists in a shift of the vibrational modes of the methylene groups CH2 and amide I, as well as in a change of their relative intensities. From the photoluminescence spectra of PA6-MWCNT, it can be seen, that the carbon nanotubes largely determine the conformational changes in the polymer matrix and have little effect on the defective structure of the polymer itself.The goal: to establish the mechanisms of electrical conductivity and the interaction of nanotubes with polyamide macromolecules and its influence on the electronic and optical properties of nanocomposites of polyamide multi-walled carbon nanotubes.

Non-volatile resistive switching behavior and time series analysis of Ag/PVA-graphene oxide/Ag device

Non-volatile memory devices have been getting significant attention from researchers worldwide in recent years due to their application in resistive random access memory and neuromorphic computing. Here, we have fabricated polyvinyl alcohol-graphene oxide (PVA-GO) composite as an active material for the resistive switching with different concentrations of GO (0.0, 0.1, 0.2, 0.3, 0.4, and 0.5 wt. % GO solution) dispersed in 5 wt. % PVA matrix in a 2:1 volume ratio. We demonstrate the non-volatile forming free resistive switching properties of Ag/PVA-GO/Ag devices. Structural properties of PVA-GO composites are established from the x-ray diffraction pattern, which indicates the complete dispersion of GO inside the PVA matrix. The Ag/PVA-GO-0.1 wt. %/Ag device shows better bipolar resistive switching at VSET ∼ 0.4 V and VRESET at ∼−0.8 V. This device indicates well-resolved two distinct states at a read voltage of 0.1 V in endurance and retention measurements. The fabricated device switches successfully tested for 2.5 × 103 cycles and retains its state for 3.36 × 103 s without any observable degradation. Furthermore, the non-volatile retention property was modeled using time series analysis. For this, Holt–Winter's exponential smoothing technique was utilized. Additionally, the charge–flux linkage characteristic shows the double-valued function, and time domain–charge and time domain–flux show asymmetric behaviors. The electrical conduction mechanism exhibits ohmic behavior in the entire region of the low resistance state and the lower voltage region of the high resistance state. In the high-voltage region of the high resistance state, the space charge-limited conduction mechanism is observed. The resistive switching behavior is explained with the help of an appropriate model.

The evaluation of the Al/ZnO/Si/Al heterojunction diode current-conducting mechanisms

This work focuses on the electrical transport and conduction mechanisms — inside a sprayed — made zinc oxide-on-p-type silicon junction device. A fabricated Al/ZnO/Si/Al heterojunction is characterized at 300 and 380[Formula: see text]K in the dark. The aforementioned theories predict that the current density (J) is an exponential function of measured voltage (V) and work temperature (T). Exponential equations are linearized as a result of a current conduction mechanism (CCM) kind. Useful parameters like barrier height [Formula: see text] of trap are extracted from the slope B. Ohmic and space charge limited current (SCLC) regimes inside are studied at 300 and 380[Formula: see text]K recording a shift in exponent as a result of temperature. Fowler–Nordheim (FN) conduction mechanism inside Al/ZnO/Si/Al device is considered slope and [Formula: see text] values are determined for two cited work temperatures. Our device presents a thermionic emission (TE) and exhibits an effect of temperature on slope and intercept values of (ln[Formula: see text]/A*[Formula: see text]) function. The Poole–Frenkel (PF) emission in terms of 1/V data are presented for 300 and 380[Formula: see text]K. Besides, PF emission mechanism in terms of 1/[Formula: see text] is exhibited and parameters are influenced by temperature. Behavior of conductance as a result of temperature is detailed and evidenced.

Microstructure correlated optical, electrical, mechanical properties and photodegradation activities of mechanically alloyed nanocrystalline Bi1.5Sb0.5Te3 as a thermoelectric material and efficient photocatalyst

Phase pure and 25 % Sb incorporated Bi2Te3 compounds with a rhombohedral crystal structure are synthesized by mechanical alloying the stoichiometric mixtures of elemental powders within 3 h under an inert atmosphere. The structure and microstructure of the synthesized samples are revealed by analyzing XRD patterns with Rietveld refinement, FESEM, HRTEM images, and EDX spectra. The increment of lattice parameter ‘c’ with increasing milling time is associated with the increased [Bi/SbTe] type antisite defects. Optical bandgaps of the pure and Sb-alloyed Bi2Te3 samples of different sizes are determined from the FTIR spectra. The transition of undoped n-type to Sb-alloyed p-type semiconducting nature is revealed from the photo responses of the samples. The ac electrical conductivity as well as complex impedance spectra in the temperature range 303–403 K reveal the semi-metallic, non-Debye type behavior of the samples and temperature-dependent relaxation phenomena. The change in electrical conductivity and the corresponding activation energies due to Sb alloying and for different grain sizes are explained in terms of antisite defects and porosity of materials. The temperature variation of the frequency exponent has been demonstrated with the small polaron hopping transaction. The Mott VRH model is used to explain the electrical conduction mechanism of the synthesized samples. The variation of Vickers microhardness with the grain size of milled samples corroborates well with the Hall-Petch relation. The normal indentation size effect (ISE) is depicted from Meyer's law. The photocatalytic activity of 10 h milled Sb-alloyed sample to degrade Rhodamine B cationic dye in wastewater is ∼ 91 %. The correlations of electrical and mechanical properties with the photocatalytic activity of the samples have been established.

High-temperature impedance properties of Sr1-xCaxTiO3 ceramics for lead-free capacitor applications

ABSTRACT Lead-free Sr0.6Ca0.4TiO3 ceramic was prepared by solid-state reaction route. X-ray diffraction technique showed the phase purity and identified the orthorhombic perovskite structure. Scanning Electronic Microscopy observation evidenced homogeneous morphology and dense microstructure. Electrical conduction and dielectric relaxation mechanisms at high temperature have been studied by complex impedance measurement techniques over a wide range of frequencies and temperatures, from 100 Hz to 1 MHz and from 573 K to 783 K. Fitting of impedance measurements allowed us to study grains and grain boundaries electrical characteristics and their contribution to the conduction and dielectric relaxation processes in the ceramic. Electrical conduction in grains is due to oxygen vacancy jumps for temperatures below 733 K and to polarons above 763 K. Electrical DC conductivity in grains and grain boundaries is mainly due to oxygen vacancies. Impedance measurements and relaxation time distribution function calculations show non-Debye-type relaxation effects for both grains and grain boundaries.

Sequential change of semiconductor mechanisms of electrical conductivity in ternary PVDF/polyaniline/MWCNT nanocomposite in the wide temperature range of 4.2–340 K

The electric charge transfer in a ternary nanocomposite based on polyaniline and multi-walled carbon nanotubes distributed in the dielectric matrix of polyvinylidene fluoride was studied in the wide temperature range of 4.2–340 K. The studied material exhibits properties similar to doped semiconductors. A sequence change in the semiconductor mechanisms of impurity conduction with increasing temperature is observed. The variable range hopping conduction dominates at helium temperatures. The excitation of charge carriers from the impurity level to the extended states provides conductivity at near room temperature. The existence of a wide transition region in the range 20–230 K, where both conduction mechanisms act simultaneously, was shown.

Influence of Fe on Crystallization Behaviour and Electrical Conductivity of V2O5 ⋅ MoO3 ⋅ CdO ⋅ ZnO Glass Nanocomposite

AbstractThe effect of varying iron content on the crystallization behavior and electrical conductivity mechanism of glass nanocomposite based on the system xFe ⋅ (1‐x) ⋅ (0.3 V2O5 ⋅ 0.2MoO3 ⋅ 0.4CdO ⋅ 0.1ZnO) (x=0.0, 0.05 and 0.1) was investigated by differential scanning calorimetry (DSC), Fourier transforms infrared (FTIR), X‐ray diffraction (XRD), and field emission‐scanning electron microscopy (FESEM). Different crystal phases and the average size of the developed nanocrystallites in the as‐prepared samples have been obtained from the XRD diffraction data. The size of estimated nanocrystallites increases up to Fe (x) content 0.05, after which the size of nanocrystallites decreases as the Fe content in the compositions increases. FESEM micrographs confirm the formation of plate‐like and dendrite nano crystallites throughout the glass matrix. Energy‐dispersive X‐ray spectroscopy (EDX) mapping analysis shows the weight percentage of each constituent element. The dc activation energy (Eσ), as well as activation energy (EH) for hopping frequency of as‐prepared samples, gradually decreases with increasing Fe content whereas AC and DC conductivity gradually increased.

Electrical conduction mechanism of carmoisine dye-based natural organic device

Electrical conduction mechanism of carmoisine dye-based natural organic device

Variable range hopping transport and dielectric relaxation mechanism in GdCrO3 rare-earth orthochromite perovskite

The polycrystalline GdCrO3 (GCO) perovskite orthochromite was synthesized by the sol–gel auto-combustion method. The Rietveld refined X-ray diffraction (XRD) profile of GCO confirms that the orthorhombic phase crystallizes in perovskite crystal structure with space group Pbnm. The transmission electron microscopy and selected area electron diffraction divulge the polycrystalline nature of the perovskite chromite. The field emission scanning electron microscopy (FESEM) images reveal the microstructural polyhedral growth of grains separated by sharp grain boundaries. The chemical states of the ions present in the compound were investigated by X-ray photoelectron spectroscopy (XPS) studies, and the electrical pathways were identified. Complex impedance studies were carried out in the experimental frequency and temperature ranges of 40 Hz–4 MHz and 178–408 K, respectively. The equivalent circuit model (RGQG) (RGBQGB) resolves the impedance response into two contributions originating from the intra-grain and inter-granular micro-constituents of the material. The electrical conduction mechanism is based on the Mott variable range hopping model. The complex electric modulus studies demonstrate the short- and long-range mobility of the charge carriers and rule out the presence of electrode effects on the dielectric relaxation mechanism of the material. The decreasing pattern of dielectric permittivity with frequency is explained by the Maxwell–Wagner type of polarization. The frequency dependence of the loss factor exhibits the presence of thermally activated relaxation time distribution in the material.

High-Temperature Dielectric Relaxation and Electric Conduction Mechanisms in a LaCoO3-Modified Na0.5Bi0.5TiO3 System.

This research study examines the high-temperature dielectric relaxation and electric conduction mechanisms in (x)LaCoO3-(1 - x)Na0.5Bi0.5TiO3 samples, where x is 0.05, 0.10, and 0.15. The findings demonstrate that all the samples exhibit two dielectric transitions: first, a frequency-dispersive shoulder at a lower temperature (Ts) around 425-450 K, which is associated with polar nanoregions (PNRs), and second, from ferroelectric to paraelectric transition at the Curie temperature (Tc) approximately between 580 and 650 K. The impedance analysis reveals the negative temperature coefficient of resistance behavior of the specimens. The broad and asymmetric relaxation peaks obtained from modulus spectroscopy demonstrate a wide range of relaxations, suggesting non-Debye-type behavior. Furthermore, the conductivity studies provide insights into understanding the transport phenomena in the samples. The oxygen vacancies resulting from the addition of LaCoO3 into the Na0.5Bi0.5TiO3 ceramics are responsible for the relaxation and conduction processes, and the charge carrier is doubly ionized oxygen ion vacancies. All samples except for LCNBT10 at 1 kHz exhibit a negative magnetodielectric response.

Process-Gas-Influenced Anti-Site Disorder and Its Effects on Magnetic and Electronic Properties of Half-Metallic Sr2FeMoO6 Thin Films

Anti-site disorder, arising due to the similar size of Fe and Mo ions in Sr2FeMoO6 (SFMO) double perovskites, hampers spintronic applicability by deteriorating the magnetic response of this double perovskite system. A higher degree of anti-site disorder can also completely destroy the half-metallicity of the SFMO system. To study the effects of different process gas conditions on the anti-site disorder, we have prepared a series of SFMO thin films on SrTiO3 (001) single-crystal substrate using a pulsed laser deposition (PLD) technique. The films are grown either under vacuum or under N2/O2 partial gas pressures. The vacuum-grown SFMO film shows the maximum value of saturation magnetization (MS) and Curie temperature (TC), signaling the lowest anti-site disorder in this series. In other words, there is a long-range Fe/Mo-O-Mo/Fe ferrimagnetic exchange in the vacuum-grown thin film, thereby enhancing the magnetization. Further, all the SFMO films show a semiconducting state with a systematic increase in overall resistivity with the increased anti-site disorder. The electrical conduction mechanism is defined by the variable-range hopping model at low temperatures. Raman spectra show a weak Fano peak, suggesting the presence of electron–phonon coupling in SFMO thin films. These results show the significance of the process gas in causing anti-site disorder, tuning the degree of this disorder and therefore its influence on the structural, magnetic, electrical, and vibrational properties of SFMO thin films.

Bi-polaron hopping process of some MoO3 doped glassy system: Efors-Shkolvshkii gap in the unoccupied states

New glassy nanocomposites, yMoO3 - (0.1 – y)V2O5 – 0.9 (0.05ZnO - 0.95CuO) is found significant not only for surveying their microstructures using X-ray diffraction, FT-IR and SEM techniques, but also for setting out to explore their electrical conduction mechanism in terms of bi-polaronhopping process. Different nanophases such as Cu4O3, ZnO, Cu3Mo2O9 etc. have been identified and the average size of estimated nanocrystallites is found to increase with MoO3content.As MoO3 content is incorporated gradually, orthorhombic phases are found to be the major phases containing TMIs. Formation of more orthorhombic phases with higher MoO3 incorporation may directly indicate the stable structure of the resultant glassy nanocomposites.Electrical conductivity of the present system has been analyzed using bi-polaron hopping process, which may take place among various localized states in the extended stable orthorhombic structures. Significant increase in density of states near Fermi level, N(EF) at higher temperature may directly indicate the expansion of the present glassy structure with more and more MoO3incorporation. All experimental data have been used to frame a schematic model to explore conduction mechanism inside the present glassy system.

Cu+ redox activation and polyselenide stabilization via strong Se-C interaction for superior magnesium storage

Copper selenides have been recognized as one of the most promising Mg2+ host materials due to their high electrical conductivity and unique ionic displacement mechanism, yet they suffer from low magnesium storage capacity and inferior cycling stability caused by insufficient Cu+ conversion and inevitable polyselenide dissolution. Herein, the graphene-supported CuSe (CuSe@G) with strong Se-C interaction is prepared as the high-performance cathode material for rechargeable magnesium batteries. The strong Se-C interaction between CuSe monomers and graphene substrate can not only immobilize the Se species but also boost the electrochemical replacement reaction between Cu2+ and Mg2+. The highly dispersed CuSe nanoparticles on graphene can also accelerate Mg2+ diffusion rate at the cathode-electrolyte interfaces and further regulate the electrochemical reaction kinetics. Such well-designed method can significantly improve the reversible capacity from 167 to 233.7 mAh g–1 at 0.1 A g–1 current density and cycling stability (63 mAh g–1 after 1000 cycles with 0.039% capacity decay per cycle) of copper selenide cathode materials. This work presents an in-depth insight into graphene bonding strategy for fabricating superior conversion-type selenide cathodes for rechargeable magnesium batteries.

Features of the Generation of Energy States in the Lu1 – xVxNiSb Semiconductor

A comprehensive study of the crystal and electronic structures, thermodynamic, kinetic, energy, and magnetic properties of the Lu1−xVxNiSb semiconductor (x = 0÷0.10) has revealed the possibility for impurity V atoms to simultaneously occupy different crystallographic positions. At the same time, defects of the acceptor or donor nature are generated in the crystal structure of the Lu1−xVxNiSb solid solution, and the corresponding energy states appear in the band gap ϵg. The concentration ratio of donor-acceptor states determines the position of the Fermi level ϵF and the mechanisms of electrical conductivity of Lu1−xVxNiSb. The results of the modeling of thermodynamic and transport properties of the semiconductor are consistent with experimental data. Understanding the mechanism of energy state generation in the semiconductor Lu1−xVxNiSb allows the modeling and production of new thermoelectric materials with a high efficiency of converting the thermal energy into the electrical one.

Absence of Weak Localization Effects in Strontium Ferromolybdate

Sr2FeMoO6-δ (SFMO) double perovskite is a promising candidate for room-temperature spintronic applications, since it possesses a half-metallic character (with theoretically 100% spin polarization), a high Curie temperature of about 415 K and a low-field magnetoresistance (LFMR). The magnetic, resistive and catalytic properties of the double perovskite SFMO are excellent for spintronic (non-volatile memory), sensing, fuel cell and microwave absorber applications. However, due to different synthesis conditions of ceramics and thin films, different mechanisms of electrical conductivity and magnetoresistance prevail. In this work, we consider the occurrence of a weak localization effect in SFMO commonly obtained in disordered metallic or semiconducting systems at very low temperatures due to quantum interference of backscattered electrons. We calculate the quantum corrections to conductivity and the contribution of electron scattering to the resistivity of SFMO. We attribute the temperature dependence of SFMO ceramic resistivity in the absence of a magnetic field to the fluctuation-induced tunneling model. We also attribute the decreasing resistivity in the temperature range from 409 K to 590 K to adiabatic small polaron hopping and not to localization effects. Neither fluctuation-induced tunneling nor adiabatic small polaron hopping favors quantum interference. Additionally, we demonstrate that the resistivity upturn behavior of SFMO cannot be explained by weak localization. Here, the fitted model parameters have no physically meaningful values, i.e., the fitted weak localization coefficient (B′) was three orders of magnitude lower than the theoretical coefficient, while the fitted exponent (n) of the electron–electron interaction term (CnTn) could not be assigned to a specific electron-scattering mechanism. Consequently, to the best of our knowledge, there is still no convincing evidence for the presence of weak localization in SFMO.